Eucocconeis flexella

This taxon has been reported with light micrographs from Alaska (Foged 1981), the northeastern US (Camburn and Charles 2000), northern Québec, Labrador (Fallu et al. 2000), Rocky Mountains, Cascades, and Olympic Mountains (Bahls 2021). It has been reported from streams of the west (EPA Western EMAP, USGS Regional Survey of California) and lakes of the northeast (EPA Northeast Lake Survey).

In the Great Lakes National Parks (Edlund et al. 2009, 2011, 2012, 2013), this taxon is common (1-5% abundance) in sediment core material from Sleeping Bear Dunes (Shell Lake). and rare (0.1-1% abundance) at Pictured Rocks (Grand Sable and Beaver lakes), Sleeping Bear Dunes (Manitou, Bass, and Florence lakes), Voyageurs (Cruiser, Ek, Little Trout, Locator lakes), and Isle Royale (Richie).

This taxon is known to occur in mountainous lakes, ponds, rivers and streams with cool waters of low conductivity and nutrient content (Bahls 2021). This taxon's pH preference is unclear (Patrick and Reimer 1966, Camburn and Charles 2000, Antoniades et al. 2008, Bahls 2021). This diatom is small in size and typically grows attached to surfaces in a prostrate manner. Cells are only slightly motile and grow as single cells (they do not form colonies). In California, this taxon is characterized within the Biological Condition Gradient (BCG) of 2, which are highly sensitive species.

Many research groups consider this taxon an indicator organism and published regional environmental optima and tolerances including:

Camburn and Charles (2000): pH - 6.66 +/- 0.78, Acid Neutralizing Capacity - 114 +/- 168 µeq/L, Total Aluminum - 107 +/- 46 µg/L, Dissolved Organic Carbon (DOC) - 382 +/- 212 µmol/L, Total Phosphorus - 6.13 +/- 3.20 µg/L for populations from the Northeastern US.

Fallu et al. (2000): DOC - 8.72 +/- 1.39 mg/L, Color - 13 +/- 2.7 Pt units, Alkalinity - 45 +/- 2.8 µeq/L for populations from northern Québec and Labrador.

Antoniades et al. (2008): pH - 8.0, Tolerance Range - 7.4-8.6, Conductivity - 128 µS/cm, Tolerance Range - 63-260 µS/cm, Dissolved Organic Carbon - 3.16 mg/L, Tolerance Range - 1.28-7.76 µS/cm for populations from the Canadian Arctic Archipelago. Note that the authors included E. leptostriata in their counts for E. flexella.

Bahls (2021): Conductivity - 224 µS/cm, pH - 7.9, Temperature - 13.8°C, Total Nitrogen - 0.19 mg/L, Total Phosphorus - 5 µg/L for populations in the Rocky Mountains, Cascades and Olympic Mountains.